In recent years, the design of mobile communication devices has become increasingly important. One feature that has become particularly popular is that of a metal cover. Such metal covers, however, can influence the radio frequency (RF) characteristics of an internal antenna of the mobile communication device.
In this regard, most mobile communication devices employ a slot type antenna. And, in order to reduce the size of such an antenna, it is typical to employ a single closed slot antenna design. A single slot design, however, can only produce a single resonant mode. As a result, where, e.g., a second, higher, band is desired for RF communication, a second harmonic generated by the slot antenna can be leveraged. Such an arrangement, however, leaves little overall control over the characteristics of the higher band, and any tuning of the lower band will almost necessarily impact the performance of the second, higher, band.
Stated alternatively, with a conventional single closed slot antenna, a low band and high band will influence each other's overall tuning. That is, with a conventional single closed slot antenna a second, higher, band cannot be independently controlled, thus reducing the communication quality of mobile communication devices with such antenna designs.